Sanofi plans to buy back up to $152 million worth of certificates linked to the success of Genzyme drugs, a move that signals its growing confidence in Lemtrada, a multiple sclerosis that is awaiting approval from regulators. The French drugmaker said on Tuesday it would buy about 30 percent of its outstanding contingent value rights (CVR) , which are linked to its 2011 purchase of U.S. biotech Genzyme, for between $130 and $152 million. Lemtrada was the main sticking point in the protracted merger talks between Sanofi and Genzyme. At the time, Sanofi Chief Executive Chris Viehbacher's team was keen to talk down its prospects. Genzyme had projected peak Lemtrada sales of $3.5 billion a year, while Sanofi pitched the number at around $700 million.